1. Field of the Invention
The present invention relates to a resin-sealed semiconductor device, and particularly relates to a resin-seal type semiconductor device having a substrate on which a semiconductor chip is mounted.
2. Description of Related Art
Along with the recent increase in power consumption and integration of semiconductor devices, semiconductor devices have come to generate more heat in operation. Since such increase in heat generated by semiconductor devices in operation causes problems such as a malfunction and a shorter lifetime of a semiconductor element, there has been strong demand for improvement in heat dissipating characteristic of semiconductor devices.
A conventionally known way of meeting such demand is use of a resin-seal type semiconductor device that is capable of efficiently dissipating heat generated therein. An example of such a resin-seal type semiconductor device is disclosed in JP-A-H11-26658.
JP-A-H11-26658 mentioned above discloses a BGA (ball grid array) type semiconductor device, which is an example of a resin-seal type semiconductor device, having a structure in which a rough surface for heat dissipation is formed on a top face of a package (a sealing resin layer). In this conventional BGA type semiconductor device, the rough shape is formed on the top face of the package (the sealing resin layer), and thus the amount of surface area of the package (the sealing resin layer) can be increased; accordingly, the amount of area of the surface of the package that is in contact with air can be increased. This makes it possible for heat generated therein to be dissipated more efficiently compared with the case where no rough shape for heat dissipation is formed.
However, in the conventional BGA type semiconductor device disclosed in the above mentioned JP-A-H11-26658, although heat dissipating characteristic is improved to some extent by forming the rough shape on the surface of the package (the sealing resin layer), in a case where a semiconductor chip that generates a larger amount of heat is mounted, it is difficult to sufficiently dissipate heat that is generated in the semiconductor chip, which is inconvenient. As a result, it is difficult to prevent a malfunction of and a decrease in lifetime of a semiconductor element, and this causes the semiconductor device to inconveniently deteriorate in reliability.